The present invention relates to a new and improved construction of multi-ply headbox.
In its more particular aspects, the present invention relates to a new and improved multi-ply headbox comprising a number of headbox elements, each of which contains an infeed member provided with turbulence elements for the fiber stock suspension and a nozzle chamber connected after the infeed member. The nozzle chambers of the headbox elements are bounded or delimited by outer lips or lip members and at least one intermediate lip or lip member located between the nozzle chambers. At least part of the lips is adjustable or displaceable for adjustment of the size of the outlet slice of the nozzle chambers.
In such general type of a multi-ply headbox as known, for example, from German Pat. No. 899,896, the intermediate lip has the shape of a tongue member which is pivotable within the nozzle chamber. Additionally, also one of the outer lips is pivotably arranged.
In such prior art headbox a precise adjustment of the size of the outlet slice, by pivoting an inner intermediate lip, can only be obtained with great difficulty, particularly considering the deformation of the lip which is to be expected across the width of the machine and considering the accuracy required for the adjustment. Furthermore, in the known headbox construction an adjustment of the intermediate lip not only affects the size of one of the outlet slices, but at the same time the size of the other outlet slice, and specifically in the converse sense. Due to the risk of deformation by torsion or twisting and the related change in the size of the two outlet slices separated from each other by the intermediate lip, such a pivotable intermediate lip must be equally loaded at both sides or faces thereof, i.e., the pressures prevailing in the two nozzle chambers must be equal.